Novel zeolite synthesis with alkaline earth metal

ABSTRACT

Provided are a novel form of AFX zeolite, a novel synthesis technique for producing pure phase small pore zeolites, a novel synthesis method for producing a zeolite with an increased Al pair content, a catalyst comprising the AFX zeolite in combination with a metal, and methods of using the same.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/402,708, filed Sep. 30, 2016.

FIELD OF INVENTION

The present invention relates to a new form of AFX having crystals witha short hexagonal prism morphology, a new form of AFX having anincreased concentration of Al pairs, novel methods for synthesizingsmall pore zeolites using an alkaline earth metal, and to the use ofsuch zeolites as catalysts for treating combustion exhaust gas.

DESCRIPTION OF RELATED ART

Zeolites are molecular sieves having unique lattice frameworksconstructed of alumina and silica cages. The Internal ZeoliteAssociation (IZA) assigns each unique framework type a three-lettercode, such as MOR, CHA, or BEA.

Synthesis of zeolite crystals typically involves reacting alumina andsilica in the presence of an organic template (also referred to as astructure directing agent or SDA; similarly, SDA cations can be referredto as SDA⁺) at elevated temperatures for several days. Duringcrystallization, the alumina and silica co-join to form a crystallinestructure around the SDA. The reactants, reaction conditions, and thespecies of SDA all impact which type or types of framework that aresynthesized. When sufficient crystallization has occurred, the crystalsare removed from the mother liquor and dried. After the crystals areseparated from the mother liquor, the organic SDA is thermally degradedand removed from the crystalline structure, thus leaving a porousmolecular sieve.

Zeolites are useful as catalyst for various industrial processes, suchas selectively reducing NO_(x) in combustion exhaust gases. Severalzeolites, such as zeolite Beta and ZSM-5, have been identified as beingparticularly useful for these types of applications. Zeolite catalystshave also been identified as being useful for hydrocarbon cracking andreforming. Typical small pore zeolites are synthesized in the presenceof alkaline metal (e.g., Na and K). However, the presence of thealkaline metal (e.g., Na) can lead to various impurities in finalproducts. For example, when AFX zeolite is synthesized in the presenceof Na⁺, mordenite zeolite can be an impurity in the final product. Inaddition, these impurities can at times affect the crystalline formsand/or may contain rod-like crystals. Thus, there is still a need for anovel and improved synthesis to produce phase pure small pore zeolites.

SUMMARY OF THE INVENTION

An aluminosilicate zeolite can comprise at least about 90% phase pureAFX framework, wherein the aluminosilicate zeolite has a short hexagonalprism morphology. The aluminosilicate zeolite can have a mean crystalsize of about 0.5 μm to about 7 μm. The aluminosilicate zeolite can havea D₉₀ crystal size of about 0.5 μm to about 7 μm, about 0.5 μm to about5 μm or about 1 μm to about 3 μm. The aluminosilicate zeolite cancomprise at least about 95% or at least about 97% phase pure AFXframework. The aluminosilicate zeolite can be free or substantially freeof medium and large pore frameworks. The aluminosilicate zeolite can befree or substantially free of zeolite Y framework. The aluminosilicatezeolite can have a silica-to-alumina ratio of about 12 to about 50,about 20 to about 40, about 20 to about 25, or about 25 to about 35. Thealuminosilicate zeolite can further comprise an alkaline earth metal.The alkaline earth metal can be selected from the group consisting ofSr, Ba, and a combination there of. The molar ratio of alkaline earthmetal to alumina can be less than about 0.1. The aluminosilicate zeolitecan be free or substantially free of alkaline metal.

A method for making an aluminosilicate zeolite having a small poreframework can comprise reacting a synthesis gel comprising at least onezeolite, a structure directing agent, an alkaline earth metal source,and an optional silica source at a temperature of at least about 100° C.until crystals of the small pore zeolite form. The crystals of the smallpore zeolite crystals can be at least about 90% phase pure. The crystalsof the small pore zeolite crystals can have an SAR of about 12 to about50. The crystals of the small pore zeolite crystals can have a meancrystal size of about 0.5 to about 7 μm. The small pore zeolite beselected from the group consisting of AFX, AEI, and CHA. The alkalineearth metal can be selected from the group consisting of Sr, Ba, and acombination thereof. The at least one zeolite can be the only silica andaluminum source. The zeolite can be zeolite Y. Zeolite Y can have asilica-to-alumina ratio of about 12 to about 60. The at least onezeolite can comprise two or more zeolites. The at least one zeolite cancomprise two or more zeolite Y. The synthesis gel can be free orsubstantially free of alkaline metal. The alkaline metal can be Na. Thesynthesis gel can have a ratio of SDA₂O/SiO₂ of less than about 1.5. Thesynthesis gel can have one or more, two or more, three or more, four ormore, five or more, or all six of the following compositional molarratios:

-   -   SiO₂/Al₂O₃ of about 10 to about 80;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.3 to about 1.5 (M_(AE) can be Ca, Sr,        or Ba);    -   SDA₂O/Al₂O₃ of about 0.7 to about 20;    -   H₂O/Al₂O₃ of about 300 to about 3000; and    -   OH⁻/SiO₂ of about 0.25 to about 0.5.

The SDA cation can be 1,3-bis(1-adamantyl)imidazolium, N,N-diethyl-cis2,6-dimethylpiperidinium, N,N-dimethyl-3,5-dimethylpiperidinium,N,N,N-1-trimethyladamantylammonium, orN,N,N-dimethylethylcyclohexylammonium. The reacting step can beperformed at a temperature of about 120-180° C. for about 3 to about 15days.

A catalyst for treating an exhaust gas comprising a pure phase AFXzeolite that comprises an extra-framework metal selected from V, Cr, Mn,Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt, and Au,wherein the zeolite has a short hexagonal prism morphology. The metalcan be Fe or Cu. The metal can be selected from Pt, Ru, and Pd.

A method for storing NO_(x) can comprise contacting an exhaust gasstream containing NO_(x) with a catalyst described herein.

A method for selectively reducing NO_(x) can comprise contacting anexhaust gas stream containing NO_(x) with a catalyst described herein.

A method for oxidizing a component of an exhaust gas can comprisecontacting an exhaust gas stream containing the component with acatalyst described herein, wherein the component is selected from CO,hydrocarbon, and NH₃.

A catalyst article can comprise a catalyst described herein supported onor incorporated into a substrate selected from a wall-flow honeycombfilter and a flow-through honeycomb substrate.

A catalyst for hydrocarbon cracking can comprise a pure phase AFXzeolite, wherein the AFX zeolite has a short hexagonal prism morphology.

A catalyst for methanol to olefin (MTO) conversion can comprise a purephase AFX zeolite, wherein the AFX zeolite has a short hexagonal prismmorphology.

A catalyst for methane to methanol conversion can comprise a pure phaseAFX zeolite, wherein the AFX zeolite has a short hexagonal prismmorphology.

A catalyst for water treatment and/or purification can comprise a purephase AFX zeolite, wherein the AFX zeolite has a short hexagonal prismmorphology.

An aluminosilicate zeolite comprising a framework comprising a number ofAl pairs that is at least twice the number of aluminum pairs in areference aluminosilicate zeolite comprising the same framework, wherethe reference aluminosilicate was synthesized using a reaction mediacomprising an alkali metal. The number of Al pairs can be determined byCo²⁺ exchange. The aluminosilicate zeolite can comprise a metal having a2+ charge, preferably Ba, Ca, Mg, Sr, or a combination thereof. Thealuminosilicate zeolite can be free or substantially free of alkalinemetal. The alkali metal can be sodium. The aluminosilicate zeolite canhave a number of Al pairs that is at least three, four, five six orseven times the number of aluminum pairs in a reference aluminosilicatezeolite comprising the same framework. The aluminosilicate zeolite canhave a framework that is a small pore framework. The framework can beAEI, AFX or CHA. The aluminosilicate zeolite can comprise at least about90%, 95% or 97% phase pure AEI, AFX or CHA framework. Thealuminosilicate zeolite can have a silica-to-alumina ratio of about 10to about 50, about 10 to about 30, or about 15 to about 25. Thealuminosilicate zeolite can comprise a first cage and a second cage andthe structure directing agent (SDA) can comprise a first SDA primarilycontained in the first cage and a second SDA primarily contained in thesecond cage in the zeolite prior to removal of the SDAs. The removal ofthe SDAs can be performed by calcination or extraction of thealuminosilicate zeolite or degradation of the SDA.

A catalytic article can comprise a substrate and an aluminosilicatezeolite comprising a framework comprising a number of Al pairs that isat least twice the number of aluminum pairs in a referencealuminosilicate zeolite comprising the same framework, where thereference aluminosilicate was synthesized using a reaction mediacomprising an alkali metal.

A system can comprise a catalytic article comprising a substrate and analuminosilicate zeolite comprising a framework comprising a number of Alpairs that is at least twice the number of aluminum pairs in a referencealuminosilicate zeolite comprising the same framework, where thereference aluminosilicate was synthesized using a reaction mediacomprising an alkali metal.

A method of making the aluminosilicate zeolite comprising a substrateand an aluminosilicate zeolite comprising a framework comprising anumber of Al pairs that is at least twice the number of aluminum pairsin a reference aluminosilicate zeolite comprising the same framework,where the reference aluminosilicate was synthesized using a reactionmedia comprising an alkali metal, can comprise reacting a synthesis gelcomprising at least one zeolite or an alkali free alumina source, astructure directing agent, an alkaline earth metal source, and anoptional silica source at a temperature of at least about 100° C. untilcrystals of the small pore zeolite form. The number of Al pairs can bedetermined by Co²⁺ exchange. The method can further comprise removingthe alkaline earth metal to form an ammonium or hydrogen form. Themethod can further comprise introducing a promoter metal into thezeolite as an extra-framework metal. The small pore zeolite crystals canbe at least about 90%, 95% or 97% phase pure. The small pore zeolitecrystals can have an SAR of about 12 to about 50. The small pore zeolitecrystals can have a mean crystal size of about 0.5 to about 7 μm. Thesmall pore zeolite can be AFX, AEI, CHA, or a combination thereof. Thealkaline earth metal can be Ba, Ca, Sr, or a combination thereof. The atleast one zeolite can be the only silica and aluminum source. Thezeolite can be zeolite Y. Zeolite Y can have a silica-to-alumina ratioof about 12 to about 60. The at least one zeolite can comprise two ormore zeolites. The at least one zeolite can comprise two or more zeoliteY. The synthesis gel can be free or substantially free of alkalinemetal, preferably the alkaline metal is Na. The synthesis gel can have aratio of SDA₂O/SiO₂ of less than about 1.5. The synthesis gel can haveone or more, two or more, three or more, four or more, five or more, orall six of the following compositional molar ratios:

-   -   SiO₂/Al₂O₃ of about 10 to about 80;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.3 to about 1.5 (M_(AE) can be Ca, Sr,        or Ba);    -   SDA₂O/Al₂O₃ of about 0.7 to about 20;    -   H₂O/Al₂O₃ of about 300 to about 3000; and    -   OH⁻/SiO₂ of about 0.25 to about 0.5.        The SDA can comprise a cation selected from the group consisting        of 1,3-bis(1-adamantyl)imidazolium, N,N-diethyl-cis        2,6-dimethylpiperidinium, N,N-dimethyl-3,5-dimethylpiperidinium,        N,N,N-1-trimethyladamantylammonium, and        N,N,N-dimethylethylcyclohexylammonium. The reacting step can be        performed at a temperature of about 120-180° C. for about 1 to        about 21 days. The method can produce an aluminosilicate zeolite        comprising a first cage and a second cage where the structure        directing agent (SDA) comprises a first SDA and a second SDA,        where the first SDA is primarily contained in the first cage and        a second SDA primarily contained in the second cage in the        zeolite prior to removal of the SDAs.

A method for increasing the number of Al pairs in an aluminosilicatezeolite comprising a framework comprising a number of Al pairs that isat least twice the number of aluminum pairs in a referencealuminosilicate zeolite comprising the same framework, where thereference aluminosilicate was synthesized using a reaction mediacomprising an alkali metal, where the method can comprise increasing theratio of alkaline earth metal source to the alkali. The step ofincreasing the ratio of alkaline earth metal source to the alkali cancomprise reacting a synthesis gel comprising at least one zeolite or analkali free alumina source, a structure directing agent, an alkalineearth metal source, and an optional silica source at a temperature of atleast about 100° C. until crystals of the small pore zeolite form.

A method of increasing the catalytic activity of a small pore zeolitecomprises forming a small pore zeolite comprising a framework having anincreased number of Al pairs compared to a comparable zeolite producedusing an alkali metal. The method can further comprise introducing apromoter metal into the zeolite as an extra-framework metal.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an XRD pattern of a pure phase AFX zeolite (JMZ-7) accordingto Example 1.

FIGS. 2a and 2b are SEM images of a pure phase AFX zeolite (JMZ-7)according to Example 1.

FIG. 3 is an SEM image of the reference AFX zeolite made with Na⁺ route(Example 2) that shows a truncated hexagonal bipyramid morphology.

FIG. 4 is an SEM image of a pure phase AEI zeolite prepared in Example3.

FIG. 5 is a graph showing the strontium content in AFX synthesized inSr²⁺ after initial synthesis followed by one and two successive NH₄exchanges as determined by ICP FIG. 6 is a graph showing the fraction ofAl in pairs for AFX synthesized in Na⁺ and AFX synthesized in Sr²⁺ asdetermined by the Co²⁺ titration method.

FIG. 7a is NO_(x) conversion profiles of fresh samples AFX.Sr—Fe andAFX.Na—Fe under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 7b is NO_(x) conversion profiles of aged samples AFX.Sr—Fe andAFX.Na—Fe under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 8a shows N₂O production profiles from fresh samples of AFX.Sr—Feand AFX.Na—Fe under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃, 14% O₂,4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalystat a space velocity of 90K/h.

FIG. 8b shows N₂O production profiles of aged samples of AFX.Sr—Fe andAFX.Na—Fe under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 9a shows NO_(x) conversion profiles of fresh samples of AFX.Sr—Feand AFX.Na—Fe under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 9b shows NO_(x) conversion profiles of aged samples of AFX.Sr—Feand AFX.Na—Fe under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 10a shows N₂O production profiles of fresh samples of AFX.Sr—Fe andAFX.Na—Fe under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂, 4.6% H₂O,5% CO₂, with the remainder being N₂ flowed over the catalyst at a spacevelocity of 90K/h.

FIG. 10b shows N₂O production profiles of aged samples of AFX.Sr—Fe andAFX.Na—Fe under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂, 4.6% H₂O,5% CO₂, with the remainder being N₂ flowed over the catalyst at a spacevelocity of 90K/h.

FIG. 11a is NO_(x) conversion profiles of a) fresh and b) aged samplesAFX.Sr—Mn and AFX.Na—Mn under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃,14% O₂, 4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed over thecatalyst at a space velocity of 90K/h.

FIG. 11b is NO_(x) conversion profiles of a) fresh and b) aged samplesAFX.Sr—Mn and AFX.Na—Mn under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃,14% O₂, 4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed over thecatalyst at a space velocity of 90K/h.

FIG. 12a shows N₂O production profiles of fresh samples AFX.Sr—Mn andAFX.Na—Mn under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 12b shows N₂O production profiles of aged samples AFX.Sr—Mn andAFX.Na—Mn under 500 ppm NO_(x) (1:1 NO:NO₂), 500 ppm NH₃, 14% O₂, 4.6%H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalyst at aspace velocity of 90K/h.

FIG. 13a shows NO_(x) conversion profiles of fresh samples AFX.Sr—Mn andAFX.Na—Mn under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂, 4.6% H₂O,5% CO₂, with the remainder being N₂ flowed over the catalyst at a spacevelocity of 90K/h.

FIG. 13b shows NO_(x) conversion profiles of aged samples AFX.Sr—Mn andAFX.Na—Mn under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂, 4.6% H₂O,5% CO₂, with the remainder being N₂ flowed over the catalyst at a spacevelocity of 90K/h.

FIG. 14a shows N₂O production profiles of fresh samples of AFX.Sr—Mn andAFX.Na—Mn samples under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂,4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalystat a space velocity of 90K/h.

FIG. 14b shows N₂O production profiles of aged samples of AFX.Sr—Mn andAFX.Na—Mn samples under 500 ppm NO_(x) (NO-only), 500 ppm NH₃, 14% O₂,4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed over the catalystat a space velocity of 90K/h.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention is directed to an aluminosilicatezeolite comprising at least about 90% phase pure AFX framework whereinthe aluminosilicate zeolite has a short hexagonal prism morphology.

As used herein, the terms “AEI”, “AFX” and “CHA” refer to an AEI, AFXand CHA framework type, respectively, as recognized by the InternationalZeolite Association (IZA) Structure Commission. The term “zeolite”refers to an aluminosilicate molecular sieve having a framework composedprimarily of alumina and silica moieties, and thus does not includeother isotypes such as SAPOs, AlPOs, and the like. As used herein, theterm “pure phase” means that at least about 90 percent of the zeoliteframework is type AFX. As used herein, the term “percent” in connectionwith the zeolite framework means:

percent crystallinity=I _(crystalline)/(I _(crystalline) +I_(amorphous))(I=intensity),

where the intensities are determined from XRD.

The impurities can be amorphous, different crystalline phases, ordifferent framework types (e.g., undissolved FAU, MOR, and/or ITE).

The AFX zeolite can contain at least about 95 percent, or even at leastabout 97 percent of the AFX framework. The AFX zeolite can besubstantially free of other crystalline phases and typically is not anintergrowth of two or more framework types.

The AFX zeolite can be substantially free of large pore frameworks. TheAFX zeolite can also be substantially free of medium pore frameworks.The AFX zeolite can be substantially free of zeolite Y, which has an FAUframework which is a large pore framework. As used herein, the term“substantially free” means that the zeolite contains less than about 10,8, 6, 4, 2, or 1 percent of the named framework or non-frameworkimpurity.

As used herein, the term “free of” a material means that that materialis not added to the process to make the aluminosilicate zeolite or thatthe material is not present at a level that is detrimental to thedesired use of the aluminosilicate zeolite.

As used herein, the term “large pore” means a framework having a maximumring size of at least 12 tetrahedral atoms, “medium pore” means aframework having a maximum ring size of at least 10 tetrahedral atoms,and the term “small pore” means a framework having a maximum ring sizeof at least 8 tetrahedral atoms.

The term “short” in connection with the hexagonal prism means thatheight of the hexagonal prism (H) is no more than base length of thehexagonal prism (B) (i.e., H/B≤1/1).

Alternatively, the aluminosilicate zeolite can comprise at least about90% phase pure AFX framework wherein the aluminosilicate zeolite has ahexagonal prism morphology with a ratio of height of the hexagonal prism(H)/base length of the hexagonal prism (B) no more than about 1/1.

AFX zeolites of the present invention can have a silica-to-alumina molarratio (SAR) of about 12 to about 50, such as about 15 to about 20, about20 to about 25, about 25 to about 30, about 30 to about 50. The SAR isbased on the synthesized zeolite crystal and not the starting synthesisgel. The silica-to-alumina ratio of zeolites can be determined byconventional analysis. This ratio is meant to represent, as closely aspossible, the ratio in the rigid atomic framework of the zeolite crystaland to exclude silicon or aluminum in the binder or in cationic or otherform within the channels. Since it can be difficult to directly measurethe silica to alumina ratio of zeolite after it has been combined with abinder material, particularly an alumina binder, these silica-to-aluminaratios are expressed in terms of the SAR of the zeolite per se, i.e.,prior to the combination of the zeolite with the other catalystcomponents.

The AFX zeolite crystals of the present invention preferably can have amean crystal size and/or a D₉₀ crystal size of about 0.5 μm to about 7μm, such as about 0.5 μm to about 2.5 μm, about 2.5 μm to about 7 μm orabout 2.5 μm to about 5 μm. The crystal size is based on individualcrystals (including twinned crystals) but does not includeagglomerations of crystals. Crystal size is the length of longestdiagonal of the three dimensional crystal. Direct measurement of thecrystal size can be performed using microscopy methods, such as SEM andTEM. For example, measurement by SEM involves examining the morphologyof materials at high magnifications (typically 1000× to 10,000×). TheSEM method can be performed by distributing a representative portion ofthe zeolite powder on a suitable mount such that individual particlesare reasonably evenly spread out across the field of view at 1000× to10,000× magnification. From this population, a statistically significantsample of random individual crystals (e.g., 50-200) are examined and thelongest diagonal of the individual crystals are measured and recorded.(Particles that are clearly large polycrystalline aggregates should notbe included the measurements.) Based on these measurements, thearithmetic mean of the sample crystal sizes is calculated.

The AFX crystals can be milled to adjust the composition's particlesize. Alternatively, the AFX crystals can be unmilled.

The aluminosilicate zeolite can further comprise an alkaline earthmetal. Examples of suitable alkaline earth metals include, but are notlimited to, Mg, Sr, Ba, Ca, and a combination thereof. Preferably thealkaline earth metal is selected from the group consisting of Sr, Ba,and a combination thereof.

The molar ratio of alkaline earth metal to alumina in thealuminosilicate zeolite can be less than about 0.1.

The aluminosilicate zeolite can further comprise an alkaline metal.Examples of suitable alkaline metals include, but are not limited to,Na, K, and a combination thereof. Preferably the alkaline metal isselected from the group consisting of Na, K, and a combination thereof.

The aluminosilicate zeolite can further comprise an alkaline earth metaland an alkaline metal.

The aluminosilicate zeolite can also be substantially free of alkalinemetal.

The aluminosilicate zeolite can also be free of alkaline metal.

The aluminosilicate zeolite can also be substantially free of analkaline earth metal.

The aluminosilicate zeolite can also be substantially free of analkaline earth metal other than Ba or Sr.

The aluminosilicate zeolite can also be free of an alkaline earth metal.

The aluminosilicate zeolite can also be free of an alkaline earth metalother than Ba or Sr.

It has been discovered that when AFX is synthesized using Sr²⁺ or Ba²⁺in an alkali free reaction mixture and the Sr²⁺ or Ba²⁺ is laterremoved, the number of Al pairs in the zeolite is greater than thenumber of Al pairs an AFX zeolite made using sodium (Na). The term “Alpairs” is defined as two Al sites that are close enough in proximitywithin the crystalline zeolite framework such that both negativeframework charges induced by Al substitution can be balanced by the sameCo²⁺ ion. Sr²⁺ or Ba²⁺ are preferably used in the reaction mixture asSr(OH)₂ or Ba(OH)² so that these hydroxide ions can provide the desiredpH for the reaction to form the zeolite. Other salts of Sr or Br, suchas chloride or nitrate, can be used. When a salt other than hydroxide isused, it may be necessary to provide a source of hydroxide to thereaction mixture to achieve the pH necessary for the aluminosilicatezeolite to form. Strontium or barium can be removed from the zeolite byvarious methods known in the art, such as one or more successiveammonium exchanges, ion-exchange or the conversion of the zeolite to aH-form. While the addition of an acid may be used in replacing the Sr orBa, it is important to prevent excessive dealumination of the zeolite.FIG. 5 shows that a sample of pure phase AFX synthesized using Sr(OH)₂(AFX.Sr) that was then calcined contained 3.21% Sr and that one ammonium(NH₄) exchange removed 98% of the Sr from AFX.Sr.

The number of Al pairs can be determined by Co²⁺ titration. (Wichterlovaet al, Phys. Chem. Chem. Phys., 2002, 4, 5406-5413)(Grounder et al,Chem. Mater. 2016. 28, 2236-2247)(Grounder et al, ACS Catal. 2017, 7,6663-6674). The number of Al pairs in a zeolite can be calculated by twomethods to determine either the absolute number of Al pairs or thenormalized number of Al pairs. The absolute number of Al pairs in thezeolite can be determined by first saturating all Al pair sites withCo²⁺ as described in Experimental Details. The Co²⁺ content in moles ofCo²⁺ per gram of zeolite can then be determined by elemental analysissuch as ICP. Each Co²⁺ can be assumed to balance two negative chargesinduced by two Al sites in a pair, thus by multiplying Co²⁺ content by afactor of two yields the number of Al sites in pairs (preferably inmmoles per gram of zeolite). This method provides a useful metric if thegoal of the material design is to maximize the number of Al in pairsites in the zeolite. The normalized number of Al pairs in the zeolitecan be determined by first measuring the total Al content by elementalanalysis such as XRF. The Al content in pair sites can then be directlydivided by the total Al content to calculate the fraction of Al in pairsites. This method provides a useful metric if the goal of the materialdesign is to maximize the number of Al in pair sites while minimizingthe number of Al in isolated sites in the zeolite. This method alsoprovides a useful way to directly compare two materials with differenttotal Al content (i.e. different SARs). FIG. 6A shows that an AFXzeolite made using Sr²⁺ had approximately 0.563 mmols of the Al as Alpairs per gram of zeolite, while an AFX zeolite made using Na⁺ had onlyapproximately 0.136 mmols of the Al as Al pairs per gram of zeolite.FIG. 6B shows that an AFX zeolite made using Sr²⁺ had approximately 40%of the Al as Al pairs, while an AFX zeolite made using Na⁺ had onlyapproximately 6% of the Al as Al pairs.

Another aspect of the present invention is directed to a method formaking an aluminosilicate zeolite having a small pore frameworkcomprising reacting a synthesis gel comprising at least one zeolite, astructure directing agent (SDA), an alkaline earth metal source, and anoptional silica source at a temperature of at least about 100° C. untilcrystals of the small pore zeolite form.

Examples of suitable small pore zeolites include, but are not limitedto, AEI, CHA, AFX, EAB, KFI, LEV, LTA, RTH, SFW, and IHW. The small porezeolite can be selected from the group consisting of AEI, CHA, AFX, EAB,KFI, and LEV. Preferably the small pore zeolite is selected from thegroup consisting of AFX, AEI, and CHA. More preferably the small porezeolite is AFX or AEI. The small pore zeolite can be CHA. The small porezeolite can be AEI. The small pore zeolite can be AFX.

The small pore zeolite crystals can be at least about 90, 95, or 97%phase pure.

The small pore zeolite crystals can have an SAR of about 12 to about 50,about 15 to about 20, about 20 to about 25, about 25 to about 30, orabout 30 to about 50.

The small pore zeolites of the present invention can be preferablyprepared with an organic SDA. Examples of suitable organic SDA cationsinclude, but are not limited to, 1,3-bis(1-adamantyl)imidazolium,N,N-diethyl-cis 2,6-dimethylpiperidinium,N,N,N-1-trimethyladamantammonium, N,N,N-dimethylethylcyclohexylammonium,and a combination thereof. Preferably the SDA cation is selected fromthe group consisting of 1,3-bis(1-adamantyl)imidazolium, N,N-diethyl-cis2,6-dimethylpiperidinium, N,N-dimethyl-3,5-dimethylpiperidinium,N,N,N-1-trimethyladamantylammonium, andN,N,N-dimethylethylcyclohexylammonium. More preferably. the SDA cationcan be 1,3-bis(1-adamantyl)imidazolium. Alternatively, or in addition,the SDA cation can be N,N-diethyl-cis 2,6-dimethylpiperidinium orN,N-dimethyl-3,5-dimethylpiperidinium. The SDA cation can beN,N,N-1-trimethyladamantylammonium. The SDA cation can beN,N,N-dimethylethylcyclohexylammonium.

The SDA cation of the present invention is typically associated withanions which can be any anion that is not detrimental to the formationof the zeolite. Representative anions include elements from Group 17 ofthe Periodic Table (e.g., fluoride, chloride, bromide and iodide),hydroxide, acetate, sulfate, tetrafluoroborate, carboxylate, and thelike.

The zeolite synthesis can be in the presence of halogens, such asfluorine.

The zeolite synthesis can be preferably free of halogens, such asfluorine.

The alkaline earth metal source can be in salt forms. The alkaline earthmetal source can also be in alkaline earth metal exchanged zeoliteforms. Examples of suitable alkaline earth metal sources include, butare not limited to, Sr(OH)₂, Ba(OH)₂, Ca(OH)₂, Sr exchanged zeolite(e.g., Sr-zeolite Y), and Ba exchanged zeolite (e.g., Ba-zeolite Y).Preferably the alkaline earth metal cation is selected from the groupconsisting of Sr, Ba, and a combination thereof.

The SDA, the at least one zeolite, the alkaline earth metal source, andan optional silica source can be mixed as prepared as a synthesis gel.The at least one zeolite can be ammonium-form zeolites, hydrogen-formzeolites, or alkaline earth metal exchanged zeolites (e.g., NH₄-formzeolite Y, H-form zeolite Y, alkaline earth metal exchanged zeolite Y).The at least one zeolite can be zeolite Y. Examples of the at least onezeolite include, but are not limited to, zeolite Y (e.g., CBV 500,CBV712, CBV720, CBV760, and CBV780). Zeolite Y can have asilica-to-alumina ratio of about 5 to about 80, about 10 to about 40, orabout 15 to about 30.

The at least one zeolite can have a lower framework density than thealuminosilicate zeolite.

The aluminosilicate zeolite of the methods of synthesis as describedabove can be CHA, wherein the SAR of the aluminosilicate zeolite can beabout 13 to about 80, about 13 to about 40, or about 30 to about 70.

The aluminosilicate zeolite of the methods of synthesis as describedabove can be AEI, wherein the SAR of the aluminosilicate zeolite can beabout 20 to about 60, about 20 to about 30, or about 30 to about 60.

The aluminosilicate zeolite of the methods of synthesis as describedabove can be AFX, the SAR of the aluminosilicate zeolite can be about 20to about 60, about 20 to about 30, or about 30 to about 60.

Examples of suitable silica sources include, but are not limited to,silica powders such as Cabosil M5 or colloid silica (Ludox), tetraalkylsilicates such as tetraethyl orthosilicate (TEOS).

The least one of the zeolites can be an alkaline earth metal exchangedzeolite (e.g., Ba-Zeolite Y, Sr-Zeolite Y), wherein the zeolite can alsobe an alkaline earth metal source of the synthesis gel.

The alkaline earth metal cation of the present invention is typicallyassociated with anions which can be any anion that is not detrimental tothe formation of the zeolite. Representative anions include elementsfrom Group 17 of the Periodic Table (e.g., fluoride, chloride, bromideand iodide), hydroxide, acetate, sulfate, tetrafluoroborate,carboxylate, and the like.

The synthesis gel of the methods of synthesis as described above canfurther comprise an alkaline metal source. Examples of suitable alkalinemetal sources include, but are not limited to, NaOH, KOH. Preferably thealkaline metal is selected from the group consisting of Na, K, and acombination thereof. More preferably the alkaline metal is Na.

The synthesis gel of the methods of synthesis as described above canfurther comprise an alkaline earth metal source and an alkaline metalsource.

The synthesis gel can also be substantially free of alkaline metal.Typically, the synthesis gel comprises less than about 4, 3, 2, or 1% ofthe alkaline metal. The alkaline metal can be Na. Unless otherwisespecified, all compositional percentages used herein are based onweight.

The synthesis gel can be free of alkaline metal.

The at least one zeolite can be the only silica and aluminum source toform the small pore zeolite.

The at least one zeolite in the synthesis gel can comprise two or morezeolites. Preferably the two or more zeolites are zeolites Y havingdifferent silica-to-alumina ratios.

The synthesis gel of the methods of synthesis as described above canhave a ratio of SDA₂O/SiO₂ of less than about 1.5.

The synthesis gel can have one or more, two or more, three or more, fouror more, five or more, or all six of the following molar compositionalratios:

-   -   SiO₂/Al₂O₃ of about 10 to about 80;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.3 to about 1.5 (M_(AE) can be Ca, Sr,        or Ba);    -   SDA₂O/Al₂O₃ of about 0.7 to about 20;    -   H₂O/Al₂O₃ of about 300 to about 3000; and    -   OH⁻/SiO₂ of about 0.25 to about 0.5.

The synthesis gel preferably can have one or more, two or more, three ormore, four or more, five or more, or all six of the following molarcompositional ratios:

-   -   SiO₂/Al₂O₃ of about 20 to about 80;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.5 to about 1.5 (M_(AE) can be Ca, Sr,        or Ba);    -   SDA₂O/Al₂O₃ of about 1 to about 6;    -   H₂O/Al₂O₃ of about 600 to about 3000; and/or    -   OH⁻/SiO₂ of about 0.25 to about 0.5.

When the aluminosilicate zeolite is CHA, the synthesis gel preferablyhas one or more, two or more, three or more, four or more, five or more,or all six of the following molar compositional ratios:

-   -   SiO₂/Al₂O₃ of about 20 to about 80;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.5 to about 1.5 (M_(AE) can be Ca, Sr,        or Ba);    -   SDA₂O/Al₂O₃ of about 1 to about 6;    -   H₂O/Al₂O₃ of about 600 to about 3000; and/or    -   OH⁻/SiO₂ of about 0.25 to about 0.5.

When the aluminosilicate zeolite is AEI, the synthesis gel preferablyhas one or more, two or more, three or more, four or more, five or more,or all six of the following molar compositional ratios:

-   -   SiO₂/Al₂O₃ of about 20 to about 60;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.5 to about 1.5 (alkaline earth metal        (M_(AE)) can be Ca, Sr, or Ba);    -   SDA₂O/Al₂O₃ of about 1 to about 6;    -   H₂O/Al₂O₃ of about 600 to about 3000; and/or    -   OH⁻/SiO₂ of about 0.25 to about 0.5.

When the aluminosilicate zeolite is AFX, the synthesis gel preferablyhas one or more, two or more, three or more, four or more, five or more,or all six of the following molar compositional ratios:

-   -   SiO₂/Al₂O₃ of about 20 to about 60;    -   Na₂O/Al₂O₃ of about 0 to about 2;    -   M_(AE)O/Al₂O₃ of about 0.5 to about 1.5 (M_(AE) can be Ca, Sr,        or Ba);    -   SDA₂O/Al₂O₃ of about 1 to about 6;    -   H₂O/Al₂O₃ of about 600 to about 3000; and/or    -   OH⁻/SiO₂ of about 0.25 to about 0.5.

The synthesis gel can also have one or more of the following molarratios: SiO₂/Al₂O₃ of about 22 to about 80; SDA₂O/Al₂O₃ of about 1 toabout 6; OH⁻/SiO₂ of about 0.25 to about 0.5.

The above synthesis method can be preferably used for making alkali freeAEI, AFX or CHA, preferably sodium free AEI, AFX or CHA, with the use ofCa, Sr or Ba as M_(AE), in place of the alkali metal, preferably inplace of sodium.

The synthesis method described above can also be used to form analuminosilicate zeolite comprising a framework comprising a number of Alpairs that is at least twice the number of aluminum pairs in a referencealuminosilicate zeolite comprising the same framework, where thereference aluminosilicate was synthesized using a reaction mediacomprising an alkali metal. The number of Al pairs can be determined byCo²⁺ exchange. In this method, there is little or no sodium. This meansthat the Na₂O/Al₂O₃ is low, about 0.

The synthesis gel can be heated to a temperature greater than 100° C.,for example about 120 to about 180° C., or about 140 to about 160° C.,for a period of time sufficient to form zeolite crystals. Thehydrothermal crystallization process is typically conducted underpressure, such as in an autoclave, and is preferably under autogenouspressure. The reaction mixture can be stirred during crystal formation.The reaction time is typically about 2 to about 15 days, for exampleabout 4 to about 8 days.

To improve selectivity for the small pore framework and/or to shortenthe crystallization process, the reaction mixture can be seeded with thesmall pore zeolite crystals. The small pore zeolite crystals can also beallowed to nucleate spontaneously from the reaction mixture.

The synthesis can be conducted in the absence of the seeded small porezeolite crystals.

Once the small pore zeolite crystals have formed, the solid product canbe separated from the mother liquor by standard mechanical separatetechniques, such as filtration. The recovered solid product can then bewashed and dried. The crystals can be thermally treated to remove theSDA, thus providing the small pore zeolite product. The small porezeolite crystals can also be calcined.

The small pore (e.g., AEI, CHA, AFX) zeolite can be used as a catalystfor various processes, such as treatment of combustion exhaust gas,hydrocarbon cracking, and conversion of methanol to an olefin (MTO), orconversion of methane to methanol. Treatable exhaust gases include thosegenerated by lean burn combustion, such as exhaust from diesel engines,gas turbines, power plants, lean burn gasoline engines, and enginesburning alternative fuels such as methanol, CNG, and the like. Othertreatable exhaust gases include those generated by rich burn engines,such as gasoline engines. The small pore zeolites can also be used inother chemical processes such as water treatment and/or purification.

A catalyst for hydrocarbon cracking can comprise a pure phase AFXzeolite, wherein the AFX zeolite has a short hexagonal prism morphology.

A catalyst for MTO (or methane to methanol) conversion can comprise apure phase AFX zeolite, wherein the AFX zeolite has a short hexagonalprism morphology.

A catalyst for methane to methanol conversion can comprise a pure phaseAFX zeolite, wherein the AFX zeolite has a short hexagonal prismmorphology.

A catalyst for water treatment and/or purification can comprise a purephase AFX zeolite, wherein the AFX zeolite has a short hexagonal prismmorphology.

The pure phase AFX zeolite in these applications is the same asdescribed above in the first aspect of the present invention and canhave the features and any combinations thereof as described above.

For the abovementioned processes, the small pore zeolite is preferablyused in heterogeneous catalytic reaction systems (i.e., solid catalystin contact with a gas reactant). To improve contact surface area,mechanical stability, and/or fluid flow characteristics, the catalystscan be disposed on and/or within a large surface area substrate, such aporous substrate. Typically, a washcoat containing the catalyst isapplied to an inert substrate, such as corrugated metal plate, pellets,a flow-through honeycomb cordierite or aluminatitanate (AT) support(brick), or a honeycomb wall-flow filter. Alternatively, the catalyst iskneaded along with other components such as fillers, binders, andreinforcing agents, into an extrudable paste which is then extrudedthrough a die to form a honeycomb brick. A catalyst article can comprisea metal-promoted small pore zeolite catalyst described herein coated onand/or incorporated into a substrate.

Small pore (e.g., AEI, CHA, AFX) zeolites according to the presentinvention can be used in combination with a promoter metal. Promotermetal should be broadly interpreted and specifically includes copper,nickel, zinc, iron, tungsten, molybdenum, cobalt, titanium, zirconium,manganese, chromium, vanadium, niobium, as well as tin, bismuth, andantimony; platinum group metals, such as ruthenium, rhodium, palladium,indium, platinum, and precious metals such as gold and silver. Preferredtransition metals are base metals, and preferred base metals includethose selected from the group consisting of chromium, manganese, iron,cobalt, nickel, and copper, and mixtures thereof. Preferably at leastone of the promoter metals is copper. Other preferred promoter metalsinclude iron, particularly in combination with copper. Preferred metalsfor converting hydrocarbons and selective reduction of NO_(x) in exhaustgas include Cu and Fe. Particularly useful metals for oxidizing CO,hydrocarbons, and/or ammonia are Pt and Pd.

The metal used in combination with the small pore (e.g., AEI, CHA, AFX)zeolite is preferably a promoter metal disposed on and/or within thezeolite material as extra-framework metals. As used herein, an“extra-framework metal” is one that resides within the molecular sieveand/or on at least a portion of the molecular sieve surface, preferablyas an ionic species, does not include aluminum, and does not includeatoms constituting the framework of the molecular sieve. Preferably, thepresence of the promoter metal(s) facilitates the treatment of exhaustgases, such as exhaust gas from a diesel engine, including processessuch as NO_(x) reduction, NH₃ oxidation, and NO_(x) storage.

The aluminosilicate zeolite produced in the synthesis gel reactiongenerally needs to have metal on the zeolite removed before a promotermetal can be added. Typically the aluminosilicate zeolite produced inthe synthesis gel reaction is first converted to an ammonia or hydrogenform of the zeolite and the promoter metal is then exchanged into thezeolite, as described herein.

The promoter metal can be present in the zeolite material at aconcentration of about 0.1 to about 10 weight percent (wt %) based onthe total weight of the zeolite, for example from about 0.5 wt % toabout 5 wt %, from about 0.5 to about 1 wt %, from about 1 to about 5 wt%, about 2.5 wt % to about 3.5 wt %. When the promoter metal is copper,iron, or the combination thereof, the concentration of these transitionmetals in the zeolite material is preferably about 1 to about 5 weightpercent, more preferably about 2.5 to about 3.5 weight percent.

The promoter metal can be present in an amount relative to the amount ofaluminum in the zeolite, namely the framework aluminum. As used herein,the promoter metal:aluminum (M:Al) ratio is based on the relative molaramount of promoter metal to molar framework Al in the correspondingzeolite. Typically, the catalyst material has a M:Al ratio of about 0.1to about 1.0, preferably about 0.2 to about 0.5. An M:Al ratio of about0.2 to about 0.5 is particularly useful where M is copper, iron ormanganese, and more particularly where M is copper, iron, or manganeseand the SAR of the zeolite is about 20 to about 25.

Preferably, incorporation of Cu occurs during synthesis or after, forexample, by ion exchange or impregnation. In one example, ametal-exchanged zeolite is synthesized within an ionic copper mixture.The metal-exchanged zeolite may then be washed, dried, and calcined.

Generally, ion exchange of the catalytic metal cation into or on themolecular sieve may be carried out at room temperature or at atemperature up to about 80° C. over a period of about 1 to 24 hours at apH of about 3 to about 7. The resulting catalytic molecular sievematerial is preferably dried at about 80 to about 120° C. overnight andcalcined at a temperature of at least about 500° C.

The catalyst composition can comprise the combination of at least onepromoter metal and at least one alkali or alkaline earth metal, whereinthe transition metal(s) and alkali or alkaline earth metal(s) aredisposed on or within the zeolite material. The alkali or alkaline earthmetal can be selected from sodium, potassium, rubidium, cesium,magnesium, calcium, strontium, barium, or some combination thereof. Asused here, the phrase “alkali or alkaline earth metal” does not mean thealkali metals and alkaline earth metals are used in the alternative, butinstead that one or more alkali metals can be used alone or incombination with one or more alkaline earth metals and that one or morealkaline earth metals can be used alone or in combination with one ormore alkali metals. Alkali metals are preferred. Alternatively, alkalineearth metals are preferred. Preferred alkali or alkaline earth metalsinclude calcium, potassium, and combinations thereof. The catalystcomposition can be essentially free of magnesium and/or barium. Thecatalyst can be essentially free of any alkali or alkaline earth metalexcept calcium and potassium. The catalyst can be essentially free ofany alkali or alkaline earth metal except calcium. The catalyst can beessentially free of any alkali or alkaline earth metal except potassium.As used herein, the term “essentially free” with respect to metal meansthat the material does not have an appreciable amount of the particularmetal. That is, the particular metal is not present in amount that wouldaffect the basic physical and/or chemical properties of the material,particularly with respect to the material's capacity to selectivelyreduce or store NO_(x).

The metal promoted zeolite catalyst composition, obtainable or obtainedby the synthesis as described in the first two aspects, can furthercomprise at least one alkali or alkaline earth metal, wherein the alkalior alkaline earth metal(s) are disposed on or within the promoter metalcontaining zeolite catalyst. The alkali or alkaline earth metal can beselected from sodium, potassium, rubidium, cesium, magnesium, calcium,strontium, barium, or some combination thereof. As used here, the phrase“alkali or alkaline earth metal” does not mean the alkali metals andalkaline earth metals are used in the alternative, but instead that oneor more alkali metals can be used alone or in combination with one ormore alkaline earth metals and that one or more alkaline earth metalscan be used alone or in combination with one or more alkali metals.Typically, alkali metals are preferred. Alternatively, alkaline earthmetals are preferred. Preferred alkali or alkaline earth metals includecalcium, potassium, and combinations thereof. The catalyst compositioncan be essentially free of magnesium and/or barium. Alternatively, thecatalyst can be essentially free of any alkali or alkaline earth metalexcept calcium and potassium. The catalyst can be essentially free ofany alkali or alkaline earth metal except calcium. The catalyst can beessentially free of any alkali or alkaline earth metal except potassium.As used herein, the term “essentially free” with respect to metal meansthat the material does not have an appreciable amount of the particularmetal. That is, the particular metal is not present in amount that wouldaffect the basic physical and/or chemical properties of the material,particularly with respect to the material's capacity to selectivelyreduce or store NO_(x).

The zeolite material can have a post-synthesis alkali/alkali-earthcontent of less than 3 weight percent, more preferably less than 1weight percent, and even more preferably less than 0.1 weight percent.Here, post-synthesis alkali content refers to the amount ofalkali/alkali-earth metal occurring in the zeolite as a result ofsynthesis (i.e., alkali/alkali-earth derived from the synthesis startingmaterials) and does not include alkali/alkali-earth metal added aftersynthesis. Typically, an alkali/alkali-earth metal can be added aftersynthesis to work in combination with the promoter metal.

The metal promoted zeolite catalysts of the present invention can alsocontain a relatively large amount of cerium (Ce). Typically, the ceriumconcentration in the catalyst material is present in a concentration ofat least about 1 weight percent, based on the total weight of thezeolite. Examples of preferred concentrations include at least about 2.5weight percent, at least about 5 weight percent, at least about 8 weightpercent, at least about 10 weight percent, about 1.35 to about 13.5weight percent, about 2.7 to about 13.5 weight percent, about 2.7 toabout 8.1 weight percent, about 2 to about 4 weight percent, about 2 toabout 9.5 weight percent, and about 5 to about 9.5 weight percent, basedon the total weight of the zeolite. Typically, the cerium concentrationin the catalyst material is about 50 to about 550 g/ft³, from about 75to about 350 g/ft³, from about 100 to about 300 g/ft³, and from about100 to about 250 g/ft³. Other ranges of Ce include: above 100 g/ft³,above 200 g/ft³, above 300 g/ft³, above 400 g/ft³, and above 500 g/ft³.

Certain aspects of the invention provide a catalytic washcoat. Thewashcoat comprising the small pore (e.g., AEI, CHA, AFX) zeolitecatalyst described herein is preferably a solution, suspension, orslurry. Suitable coatings include surface coatings, coatings thatpenetrate a portion of the substrate, coatings that permeate thesubstrate, or some combination thereof.

In general, the production of an extruded solid body containing themetal promoted small pore (e.g., AEI, CHA, AFX) zeolite catalystinvolves blending the small pore (e.g., AEI, CHA, AFX) zeolite and thepromoter metal (either separately or together as a metal-exchangedzeolite), a binder, an optional organic viscosity-enhancing compoundinto an homogeneous paste which is then added to a binder/matrixcomponent or a precursor thereof and optionally one or more ofstabilized ceria, and inorganic fibers. The blend is compacted in amixing or kneading apparatus or an extruder. The mixtures have organicadditives such as binders, pore formers, plasticizers, surfactants,lubricants, dispersants as processing aids to enhance wetting andtherefore produce a uniform batch. The resulting plastic material isthen molded, in particular using an extrusion press or an extruderincluding an extrusion die, and the resulting moldings are dried andcalcined. The organic additives are “burnt out” during calcinations ofthe extruded solid body. A metal-promoted small pore (e.g., AEI, CHA,AFX) zeolite catalyst may also be washcoated or otherwise applied to theextruded solid body as one or more sub-layers that reside on the surfaceor penetrate wholly or partly into the extruded solid body.Alternatively, a metal-promoted small pore (e.g., AEI, CHA, AFX) zeolitecan be added to the paste prior to extrusion.

Extruded solid bodies containing metal-promoted small pore (e.g., AEI,CHA, AFX) zeolites according to the present invention generally comprisea unitary structure in the form of a honeycomb having uniform-sized andparallel channels extending from a first end to a second end thereof.Channel walls defining the channels are porous. Typically, an external“skin” surrounds a plurality of the channels of the extruded solid body.The extruded solid body can be formed from any desired cross section,such as circular, square or oval. Individual channels in the pluralityof channels can be square, triangular, hexagonal, circular etc. Channelsat a first, upstream end can be blocked, e.g. with a suitable ceramiccement, and channels not blocked at the first, upstream end can also beblocked at a second, downstream end to form a wall-flow filter.Typically, the arrangement of the blocked channels at the first,upstream end resembles a checker-board with a similar arrangement ofblocked and open downstream channel ends.

The binder/matrix component is preferably selected from the groupconsisting of cordierite, nitrides, carbides, borides, intermetallics,lithium aluminosilicate, a spinel, an optionally doped alumina, a silicasource, titania, zirconia, titania-zirconia, zircon and mixtures of anytwo or more thereof. The paste can optionally contain reinforcinginorganic fibers selected from the group consisting of carbon fibers,glass fibers, metal fibers, boron fibers, alumina fibers, silica fibers,silica-alumina fibers, silicon carbide fibers, potassium titanatefibers, aluminum borate fibers and ceramic fibers.

The alumina binder/matrix component is preferably gamma alumina, but canbe any other transition alumina, i.e., alpha alumina, beta alumina, chialumina, eta alumina, rho alumina, kappa alumina, theta alumina, deltaalumina, lanthanum beta alumina and mixtures of any two or more suchtransition aluminas. It is preferred that the alumina is doped with atleast one non-aluminum element to increase the thermal stability of thealumina. Suitable alumina dopants include silicon, zirconium, barium,lanthanides and mixtures of any two or more thereof. Suitable lanthanidedopants include La, Ce, Nd, Pr, Gd and mixtures of any two or morethereof.

Sources of silica can include a silica sol, quartz, fused or amorphoussilica, sodium silicate, an amorphous aluminosilicate, an alkoxysilane,a silicone resin binder such as methylphenyl silicone resin, a clay,talc or a mixture of any two or more thereof. Of this list, the silicacan be SiO₂ as such, feldspar, mullite, silica-alumina, silica-magnesia,silica-zirconia, silica-thoria, silica-berylia, silica-titania, ternarysilica-alumina-zirconia, ternary silica-alumina-magnesia,ternary-silica-magnesia-zirconia, ternary silica-alumina-thoria andmixtures of any two or more thereof.

Preferably, the metal-promoted small pore (e.g., AEI, CHA, AFX) zeoliteis dispersed throughout, and preferably evenly throughout, the entireextruded catalyst body.

Where any of the above extruded solid bodies are made into a wall-flowfilter, the porosity of the wall-flow filter can be from about 30% toabout 80%, such as from 40% to about 70%. Porosity and pore volume andpore radius can be measured e.g. using mercury intrusion porosimetry

The metal-promoted small pore (e.g., AEI, CHA, AFX) catalyst describedherein can promote the reaction of a reductant, preferably ammonia, withnitrogen oxides to selectively form elemental nitrogen (N₂) and water(H₂O). The catalyst can be formulated to favor the reduction of nitrogenoxides with a reductant (i.e., an SCR catalyst). Examples of suchreductants include hydrocarbons (e.g., C₃-C₆ hydrocarbons) andnitrogenous reductants such as ammonia and ammonia hydrazine or anysuitable ammonia precursor, such as urea ((NH₂)₂CO), ammonium carbonate,ammonium carbamate, ammonium hydrogen carbonate or ammonium formate.

An aluminosilicate zeolite comprising a framework comprising a number ofAl pairs that greater than the number of aluminum pairs in a referencealuminosilicate zeolite comprising the same framework formed using analkali metal can also be used in any of the uses described herein.Preferably, the aluminosilicate zeolite comprising the higher number ofAl pairs also contains one or more extra-framework metals, as describedherein. The use of these zeolites can provide improved NO_(x)conversion, less N₂O formation, etc. as described herein.

The metal-promoted small pore (e.g., AEI, CHA, AFX) catalyst describedherein can also promote the oxidation of ammonia. Typically, thecatalyst can be formulated to favor the oxidation of ammonia withoxygen, particularly a concentrations of ammonia typically encountereddownstream of an SCR catalyst (e.g., ammonia oxidation (AMOX) catalyst,such as an ammonia slip catalyst (ASC)). The metal-promoted small pore(e.g., AEI, CHA, AFX) zeolite catalyst can be disposed as a top layerover an oxidative under-layer, wherein the under-layer comprises aplatinum group metal (PGM) catalyst or a non-PGM catalyst. Preferably,the catalyst component in the underlayer is disposed on a high surfacearea support, including but not limited to alumina.

SCR and AMOX operations can be performed in series, wherein bothprocesses utilize a catalyst comprising the metal-promoted small pore(e.g., AEI, CHA, AFX) zeolite described herein, and wherein the SCRprocess occurs upstream of the AMOX process. For example, an SCRformulation of the catalyst can be disposed on the inlet side of afilter and an AMOX formulation of the catalyst can be disposed on theoutlet side of the filter.

Accordingly, provided is a method for the reduction of NO_(x) compoundsor oxidation of NH₃ in a gas, which comprises contacting the gas with acatalyst composition described herein for the catalytic reduction ofNO_(x) compounds for a time sufficient to reduce the level of NO_(x)compounds and/or NH₃ in the gas. Typically, a catalyst article having anammonia slip catalyst is disposed downstream of a selective catalyticreduction (SCR) catalyst. The ammonia slip catalyst oxidizes at least aportion of any nitrogenous reductant that is not consumed by theselective catalytic reduction process. Typically, the ammonia slipcatalyst is disposed on the outlet side of a wall flow filter and an SCRcatalyst is disposed on the upstream side of a filter. Alternatively,the ammonia slip catalyst is disposed on the downstream end of aflow-through substrate and an SCR catalyst is disposed on the upstreamend of the flow-through substrate. The ammonia slip catalyst and SCRcatalyst can be disposed on separate substrates (bricks) within theexhaust system. These separate bricks can be adjacent to, and in contactwith, each other or separated by a specific distance, provided that theyare in fluid communication with each other and provided that the SCRcatalyst brick is disposed upstream of the ammonia slip catalyst brick.

The SCR and/or AMOX process can be performed at a temperature of atleast 100° C. The process(es) can occur at a temperature from about 150°C. to about 750° C. Preferably the temperature range is from about 175to about 550° C. or from about 175 to about 400° C. Alternatively, thetemperature range is about 450 to about 900° C., preferably about 500 toabout 750° C., about 500 to about 650° C., about 450 to about 550° C.,or about 650 to about 850° C. Temperatures greater than about 450° C.are particularly useful for treating exhaust gases from a heavy or lightduty diesel engine that is equipped with an exhaust system comprising(optionally catalyzed) diesel particulate filters which are regeneratedactively, e.g. by injecting hydrocarbon into the exhaust system upstreamof the filter, wherein the zeolite catalyst for use in the presentinvention is located downstream of the filter.

According to another aspect of the invention, provided is a method forthe reduction of NO_(X) compounds and/or oxidation of NH₃ in an exhaustgas, which comprises contacting the exhaust gas with a catalystdescribed herein in the presence of a reducing agent for a timesufficient to reduce the level of NO_(X) compounds in the gas. Thesemethods can further comprise one or more of the following steps: (a)accumulating and/or combusting soot that is in contact with the inlet ofa catalytic filter; (b) introducing a nitrogenous reducing agent intothe exhaust gas stream prior to contacting the catalyst in an SCRfilter, preferably with no intervening catalytic steps involving thetreatment of NO_(x) and the reductant; (c) generating NH₃ over a NO_(x)adsorber catalyst or lean NO_(x) trap, and preferably using such NH₃ asa reductant in a downstream SCR reaction; (d) contacting the exhaust gasstream with a DOC to oxidize hydrocarbon based soluble organic fraction(SOF) and/or carbon monoxide into CO₂, and/or oxidize NO into NO₂, whichin turn, can be used to oxidize particulate matter in particulatefilter; and/or reduce the particulate matter (PM) in the exhaust gas;and (e) contacting the exhaust gas with an ammonia slip catalyst,preferably downstream of the SCR catalyst to oxidize most, if not all,of the ammonia prior to emitting the exhaust gas into the atmosphere orpassing the exhaust gas through a recirculation loop prior to exhaustgas entering/re-entering the engine.

All or at least a portion of the nitrogen-based reductant, particularlyNH₃, for consumption in the SCR process can be supplied by a NO_(x)adsorber catalyst (NAC), a lean NO_(x) trap (LNT), or a NO_(x)storage/reduction catalyst (NSRC), disposed upstream of the SCRcatalyst, e.g., an SCR catalyst of the present invention disposed on awall-flow filter. NAC components useful in the present invention includea catalyst combination of a basic material (such as alkali metal,alkaline earth metal or a rare earth metal, including oxides of alkalimetals, oxides of alkaline earth metals, and combinations thereof), anda precious metal (such as platinum), and optionally a reduction catalystcomponent, such as rhodium. Specific types of basic material useful inthe NAC include cesium oxide, potassium oxide, magnesium oxide, sodiumoxide, calcium oxide, strontium oxide, barium oxide, and combinationsthereof. The precious metal is preferably present at about 10 to about200 g/ft³, such as about 20 to about 60 g/ft³. Alternatively, theprecious metal of the catalyst is characterized by the averageconcentration which can be from about 40 to about 100 grams/ft³.

Under certain conditions, during the periodically rich regenerationevents, NH₃ can be generated over a NO_(x) adsorber catalyst. The SCRcatalyst downstream of the NO_(x) adsorber catalyst can improve theoverall system NO_(x) reduction efficiency. In the combined system, theSCR catalyst is capable of storing the released NH₃ from the NACcatalyst during rich regeneration events and utilizes the stored NH₃ toselectively reduce some or all of the NO_(x) that slips through the NACcatalyst during the normal lean operation conditions.

The method for treating exhaust gas as described herein can be performedon an exhaust gas derived from a combustion process, such as from aninternal combustion engine (whether mobile or stationary), a gas turbineand coal or oil fired power plants. The method may also be used to treatgas from industrial processes such as refining, from refinery heatersand boilers, furnaces, the chemical processing industry, coke ovens,municipal waste plants and incinerators, etc. Typically, the method isused for treating exhaust gas from a vehicular lean burn internalcombustion engine, such as a diesel engine, a lean-burn gasoline engineor an engine powered by liquid petroleum gas or natural gas.

In certain aspects, the invention is a system for treating exhaust gasgenerated by combustion process, such as from an internal combustionengine (whether mobile or stationary), a gas turbine, coal or oil firedpower plants, and the like. Such systems include a catalytic articlecomprising the metal-promoted small pore (e.g., AEI, CHA, AFX) zeolitedescribed herein and at least one additional component for treating theexhaust gas, wherein the catalytic article and at least one additionalcomponent are designed to function as a coherent unit.

The system can comprise a catalytic article comprising a metal-promotedsmall pore (e.g., AEI, CHA, AFX) zeolite described herein, a conduit fordirecting a flowing exhaust gas, a source of nitrogenous reductantdisposed upstream of the catalytic article. The system can include acontroller for the metering the nitrogenous reductant into the flowingexhaust gas only when it is determined that the zeolite catalyst iscapable of catalyzing NO_(x) reduction at or above a desired efficiency,such as at above 100° C., above 150° C. or above 175° C. The metering ofthe nitrogenous reductant can be arranged such that 60% to 200% oftheoretical ammonia is present in exhaust gas entering the SCR catalystcalculated at 1:1 NH₃/NO and 4:3 NH₃/NO₂.

The system can comprise an oxidation catalyst (e.g., a diesel oxidationcatalyst (DOC)) for oxidizing nitrogen monoxide in the exhaust gas tonitrogen dioxide can be located upstream of a point of metering thenitrogenous reductant into the exhaust gas. The oxidation catalyst canbe adapted to yield a gas stream entering the SCR zeolite catalysthaving a ratio of NO to NO₂ of from about 4:1 to about 1:3 by volume,e.g. at an exhaust gas temperature at oxidation catalyst inlet of 250°C. to 450° C. The oxidation catalyst can include at least one platinumgroup metal (or some combination of these), such as platinum, palladium,or rhodium, coated on a flow-through monolith substrate. The at leastone platinum group metal can be platinum, palladium or a combination ofboth platinum and palladium. The platinum group metal can be supportedon a high surface area washcoat component such as alumina, a zeolitesuch as an aluminosilicate zeolite, silica, non-zeolite silica alumina,ceria, zirconia, titania or a mixed or composite oxide containing bothceria and zirconia.

A suitable filter substrate can be located between the oxidationcatalyst and the SCR catalyst. Filter substrates can be selected fromany of those mentioned above, e.g. wall flow filters. Where the filteris catalyzed, e.g. with an oxidation catalyst of the kind discussedabove, preferably the point of metering nitrogenous reductant is locatedbetween the filter and the zeolite catalyst. Alternatively, if thefilter is un-catalyzed, the means for metering nitrogenous reductant canbe located between the oxidation catalyst and the filter.

The metal-promoted small pore zeolite (e.g., AEI, CHA, AFX) catalystdescribed herein can also be a passive NO_(x) absorber (PNA) catalyst(i.e. it has PNA activity). Such a catalyst can be prepared according tothe method described in WO 2012/166868 (also published as U.S.2012308439) (both of which are hereby incorporated by reference), andthe promoter metal can comprise a noble metal.

The noble metal is typically selected from the group consisting ofpalladium (Pd), platinum (Pt), rhodium (Rh), gold (Au), silver (Ag),iridium (Ir), ruthenium (Ru) and mixtures of two or more thereof.Preferably, the noble metal is selected from the group consisting ofpalladium (Pd), platinum (Pt) and rhodium (Rh). More preferably, thenoble metal is selected from palladium (Pd), platinum (Pt) and a mixturethereof.

Generally, it is preferred that the noble metal comprises, or consistsof, palladium (Pd) and optionally a second metal selected from the groupconsisting of platinum (Pt), rhodium (Rh), gold (Au), silver (Ag),iridium (Ir) and ruthenium (Ru). Preferably, the noble metal comprises,or consists of, palladium (Pd) and optionally a second metal selectedfrom the group consisting of platinum (Pt) and rhodium (Rh). Morepreferably, the noble metal comprises, or consists of, palladium (Pd)and optionally platinum (Pt). Even more preferably, the catalystcomprises palladium as the only noble metal.

When the noble metal comprises, or consists of, palladium (Pd) and asecond metal, then the ratio by mass of palladium (Pd) to the secondmetal is >1:1. Preferably, the ratio by mass of palladium (Pd) to thesecond metal is >1:1 and the molar ratio of palladium (Pd) to the secondmetal is >1:1. The aforementioned ratio of palladium relates to theamount of palladium present as part of the PNA catalyst. It does notinclude any palladium that may be present on the support material. ThePNA catalyst can further comprise a base metal. Thus, the PNA catalystcan comprise, or consist essentially of, a noble metal, a small porezeolite as described herein and optionally a base metal. The base metalcan be selected from the group consisting of iron (Fe), copper (Cu),manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni), zinc (Zn) andtin (Sn), as well as mixtures of two or more thereof. It is preferredthat the base metal is selected from the group consisting of iron,copper and cobalt, more preferably iron and copper. Even morepreferably, the base metal is iron.

Alternatively, the PNA catalyst can be free or substantially free of abase metal, such as a base metal selected from the group consisting ofiron (Fe), copper (Cu), manganese (Mn), chromium (Cr), cobalt (Co),nickel (Ni), zinc (Zn) and tin (Sn), as well as mixtures of two or morethereof.

In general, it is preferred that the PNA catalyst does not comprise abase metal.

It can be preferable that the PNA catalyst is substantially free ofbarium (Ba), more preferably the PNA catalyst is substantially free ofan alkaline earth metal. Thus, the PNA catalyst may not comprise barium,preferably the PNA catalyst does not comprise an alkaline earth metal.

Although the description above contains many specifics, these are merelyprovided to illustrate the invention and should not be constructed aslimitations of the invention's scope. It should be also noted that manyspecifics could be combined in various ways in a single or multipleembodiments. Thus it will be apparent to those skilled in the art thatvarious modifications and variations can be made in the compositions,processes, catalysts, and methods of the present invention withoutdeparting from the spirit or scope of the invention.

EXAMPLES

Materials produced in the examples described below were characterized byone or more of the following analytic methods. Powder X-ray diffraction(PXRD) patterns were collected on a X'pert (Philips) or Bruker D8 powderdiffractometer using a CuKα radiation (40-45 kV, 40 mA) at a step sizeof 0.04° and a 1 s per step between 5° and 40° (2θ). Scanning electronmicroscopy (SEM) images and chemical compositions by energy-dispersiveX-ray spectroscopy (EDX) were obtained on a JEOL JSM7400F and Auriga 60CrossBeam (FIB/FE-SEM) microscopes, operating at an acceleration voltageof 1.5-3 keV, and a current of 10 μA. The micropore volume and surfacearea were measured using N₂ at 77 K on a 3Flex surface characterizationanalyzer (Micrometrics).

Reagents:

Zeolite Y (CBV720 (SAR-30-32) from Zeolyst), DI water,1,3-bis(1-adamantyl) imidazolium hydroxide (BAI-OH, 18% wt), Sr(OH)₂(94%, Sigma), NaOH 1N (diluted from NaOH 99%, Fisher Scientific),2,6-N,N-diethyl-cis 2,6-dimethylpiperidinium hydroxide (2,6-DMP-OH, 22%wt)

Example 1: Synthesis of JMZ-7

6.1 g of BAI-OH, 18 wt % was mixed with 0.07 g of Sr(OH)₂ and 1.91 g ofwater. Next, 1.04 g of zeolite Y (CBV 720, Zeolyst) having an SAR of˜30-32 was added to the mixture under stirring for 5 minutes. Themixture was then heated at 155° C. under rotation (45 rpm) for 6 days.

To obtain the AFX powder product, the autoclaves were cooled to roomtemperature in air and the crystalline product was recovered byfiltration, washed several times with deionized water and dried at 80°C. overnight in a drying oven. The as-made product (JMZ-7) was calcinedat 580° C./8 hours in air with ramping rate of 3° C./min.

Samples of the dried product were analysed by XRD, SEM, EDX, and N₂adsorption as described above. Analysis of the as-made product by powderXRD (FIG. 1) indicated that the product had an AFX structure. SEM imagesof the as-made sample (FIGS. 2a and 2b ) showed that it had a shorthexagonal prism morphology. An N₂ adsorption measurements of thecalcined product had a BET surfaces area of ˜650 m²/g, a pore volume of˜0.27 cm³/g. The calcined product had an SAR of about 30.

Example 2: Synthesis of Reference AFX

A reference AFX zeolite having an SAR ratio of about 22 was synthesizedaccording to Example 1 in US 20160137518 Al via Na⁺ route. FIG. 3 is anSEM image of the reference AFX zeolite, which had a truncated hexagonalbipyramid morphology.

Example 3: Synthesis of AEI

10.5 g of the 2,6-DMP-OH (22 wt %) was mixed with 0.22 g of Sr(OH)₂ and5.8 g of water. Then, the mixture was stirred for about 5 minutes. 2.36g of zeolite Y (CBV 720, Zeolyst) having an SAR of ˜30-32 was added tothe mixture under stirring for another 5 minutes. The mixture was thenheated at 155° C. under rotation (45 rpm) for 5 days.

To obtain the AEI powder product, the autoclaves were cooled to roomtemperature in air and the crystalline product was recovered byfiltration, washed several times with deionized water and dried at 80°C. overnight in a drying oven. The as-made product was calcined at 580°C./8 hours in air with ramping rate of 3° C./min.

Samples of the dried product were analysed by XRD, N₂ adsorption, EDX,and SEM as described above. Analysis of the as-made product by powderXRD indicated that the product had an AEI structure. An N₂ adsorptionmeasurements of the calcined product showed that the product had a BETsurfaces area of ˜670 m²/g, a pore volume of ˜0.26 cm³/g. An SEM imageof the as-made sample (FIG. 4) showed that it had a cuboid morphology.The calcined product had an SAR of about 30.

TABLE 1 Synthesis Gel Composition of Example 3 Recipe H₂O Al₂O₃ SiO₂Sr(OH)₂ 2,6-DMP-OH Mole ratios 24 0.0333 1 0.05 0.35

Example 4. Strontium Removal from AFX.Sr by Ammonium-Exchange

The strontium content of AFX synthesized in Sr²⁺ after initial synthesisfollowed by one and two successive ammonium exchanges is displayed inFigure X. A solution containing 0.42 M NH₄₊ was prepared by dissolvingthe appropriate amount of ammonium nitrate (Seidler Chemical Company) inde-mineralised water. To this NH₄₊ solution, the Sr²⁺ or Na⁺ containingAFX.Sr and AFX.Na (both samples have template removed) were added in aratio of 30 mL of NH₄ solution per 1 g of zeolite. The zeolite and NH₄containing solution was heated to ˜70° C. with stirring for a few hours.The zeolite was then filtered out of solution and washed with excessde-mineralised water to remove any non-exchanged NH₄. This exchangeprocess was repeated multiple times in succession until the Sr²⁺ or Na⁺content in the zeolite (as measured by ICP) was removed (typically 1-2exchanges).

Example 5. Cobalt Exchanges for Al Pair Titration

A solution containing 0.05 M Co²⁺ was prepared by dissolving theappropriate amount of cobalt (II) nitrate hexahydrate (Alfa Aesar) inde-mineralised water. To this Co²⁺ solution, the H-forms of AFX.Sr—H andAFX.Na—H (both samples have template and alkali/alkali earth metalremoved) were added in a ratio of 50 mL of Co²⁺ solution per 1 g ofzeolite. The zeolite and Co²⁺ containing solution was heated to ˜70° C.with stirring for a few hours. The zeolite was then filtered out ofsolution and washed with excess de-mineralised water to remove anynon-exchanged Co²⁺. This exchange process was repeated multiple times insuccession until the Co²⁺ content in the zeolite (as measured by ICP) nolonger increased (typically 3-5 exchanges).

The quantity of Al pair sites in each of the two materials wasdetermined by the Co²⁺ titration method is displayed in Figure X. Co²⁺will only exchange at Al pair sites in zeolites as has been rigorouslydetermined by prior literature (Wichterlovi and co-workers, Phys. Chem.Chem. Phys. 2002, 4, 5406-5413. Gounder and co-workers, Chem. Mater.2016, 28, 2236-2247. Gounder and co-workers, ACS Catal. 2017, 7,6663-6674.). Al pairs in this instance are defined as two Al sites thatare close enough in proximity within the crystalline zeolite frameworksuch that both negative framework charges induced by Al substitution canbe balanced by the same Co²⁺ ion. Therefore, Co²⁺ exchange capacity wasused to quantify the number of Al pair sites in AFX synthesized in Sr²⁺compared to AFX synthesized in Na⁺. The number of Al in pair sites wasthen normalized on total Al content (determined by XRF) in each materialand given as a fraction of the total sites. AFX.Sr—H contained 41% of Alsites as Al pairs whereas AFX.Na—H only contained 6% of Al sites as Alpairs. Normalization was conducted because of a potential difference inthe SAR between the two zeolites.

Example 6. Catalyst Testing of Fe-Exchanged AFX for Fast and StandardNH₃ SCR

Ammonium-exchanged and calcined AFX.Sr—H and AFX.Na—H (both samples havetemplate and alkali removed) were impregnated with iron at a loading of3.33 wt % using the required amount of ferric nitrate nonahydrate (VWR)dissolved in de-mineralised water. The Fe-impregnated AFX.Sr—H andAFX.Na—H samples (designated AFX.Sr—Fe and AFX.Na—Fe, respectively) weredried overnight at 80° C. and then calcined in air at 550° C. for 4hours.

Samples of the powdered catalyst were pelletized and then aged in a flowof 10% H₂O in air. The samples were heated at a rate of 10° C./min to250° C. in air only. The samples were then heated at a rate of 10°C./min in 10% H₂O in air to 550° C. After being held at a temperature of550° C. for 100 hours, the samples were cooled in the steam/air mixtureuntil then temperature was <250° C. The samples were then cooled from250° C. to room temperature in an air only flow.

Pelletized samples of the powder catalyst were tested in an apparatus inwhich a gas comprising 500 ppm NO_(x) (NO-only or 1:1 NO:NO₂), 500 ppmNH₃, 14% O₂, 4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed overthe catalyst at a space velocity of 90K/h. The samples were heated fromroom temperature to 150° C. under the above mentioned gas mixture exceptfor NH₃. At 150° C., NH₃ was added in to the gas mixture and the sampleswere held under these conditions for 30 min. The temperature was thenincreased (ramped) from 150 to 500° C. at 5° C./minute.

Fresh and aged NO_(x) (1:1 NO:NO₂) conversion activity profiles overtemperatures from 150° C. to 500° C. are given in FIGS. 7A and 7B. Theactivity of fresh AFX.Sr—Fe exhibited a T50 (the temperature at which50% conversion of NO_(x) is achieved) of 273° C. which was 22° C. lowerthan the T50 of AFX.Na—Fe (295° C.). Furthermore, AFX.Sr—Fe displayedenhanced NO_(x) conversions up to 35% higher than AFX.Na—Fe attemperatures <360° C. At temperatures >360° C., AFX.Sr—Fe and AFX.Na—Feachieved similar NO_(x) conversions (>95%). Both samples exhibitedenhanced NO_(x) conversion after aging, with both samples being affectedequally. The aged sample of AFX.Sr—Fe once again demonstrated a lowerT50 at 250° C. than AFX.Na—Fe at 273° C. Moreover, AFX.Sr—Fe showedenhanced NO_(x) conversions up to 35% higher than AFX.Na—Fe attemperatures <295° C. At temperatures >295° C., AFX.Sr—Fe and AFX.Na—Feachieved similar NO_(X) conversions (˜95%).

The concentration of N₂O in gas passing through fresh and aged catalystsover temperatures from 150° C. to 500° C. are given in FIGS. 8A and 8B.Gas flowing into the apparatus contained 500 ppm NO_(x) as 1:1 NO:NO₂.In the fresh samples, AFX.Sr—Fe produced significantly less N₂O (peakvalue of 10 ppm) than AFX.Na—Fe (peak value of 60 ppm) over the entiretemperature range. After aging, the N₂O levels for both AFX.Sr—Fe andAFX.Na—Fe decreased significantly. However, AFX.Sr—Fe still produced asignificantly less N₂O (peak value of 5 ppm) than AFX.Na—Fe (peak valueof 11 ppm) in the 150° C. to 300° C. temperature regime. Only in therange of 325-500° C. did the AFX.Sr—Fe and AFX.Na—Fe produce similaramounts of N₂O after aging.

Fresh and aged NO_(x) (NO-only) conversion activity profiles overtemperatures from 150° C. to 500° C. are given in FIGS. 9A and 9B. Theactivity of fresh AFX.Sr—Fe exhibited a T50 of 390° C. which was 55° C.lower than the T50 of AFX.Na—Fe (445° C.). Furthermore, AFX.Sr—Feexhibited enhanced NO_(x) conversion compared to AFX.Na—Fe across theentire temperature range (150-500° C., up to 25% higher NO_(x)conversion). Both samples exhibited reduced NO_(x) conversion afteraging, however, both samples were not affected equally. The aged sampleof AFX.Sr—Fe exhibited a T50 of 395° C. which was only 5° C. higher thanthe fresh sample. The T50 of the aged AFX.Na—Fe, however, was delayedsignificantly to 485° C. (40° C. higher than the fresh sample).Additionally, aged AFX.Sr—Fe achieved higher NO_(x) conversions (up to17% higher) than AFX.Na—Fe over the entire temperature range.

The concentration of N₂O in gas passing through fresh and aged catalystsover temperatures from 150° C. to 500° C. are given in FIGS. 10A and10B. Gas flowing into the apparatus contained 500 ppm NO_(x) as NO only.In the fresh samples, AFX.Sr—Fe produced less N₂O (peak value of 2.5ppm) than AFX.Na—Fe (peak value of 4.8 ppm) over the entire temperaturerange. After aging, the N₂O levels for both AFX.Sr—Fe and AFX.Na—Fedecreased slightly. However, AFX.Sr—Fe still produced less N₂O (peakvalue of 2 ppm) than AFX.Na—Fe (peak value of 3.5 ppm) over the entiretemperature range.

Example 7. Catalyst Testing of Mn-Exchanged AFX for Fast and StandardNH₃ SCR

Ammonium-exchanged and calcined AFX.Sr—H and AFX.Na—H (both samples havetemplate and alkali removed) were impregnated with manganese at aloading of 3.33 wt % using the required amount of manganese (II) acetate(Umicore) dissolved in de-mineralised water. The Mn-impregnated AFX.Sr—Hand AFX.Na—H samples (designated AFX.Sr—Mn and AFX.Na—Mn, respectively)were dried overnight at 80° C. and then calcined in air at 550° C. for 4hours.

Samples of the powdered catalyst were pelletized and then aged in a flowof 10% H₂O in air. The samples were heated at a rate of 10° C./min to250° C. in air only. The samples were then heated at a rate of 10°C./min in 10% H₂O in air to 550° C. After being held at a temperature of550° C. for 100 hours, the samples were cooled in the steam/air mixtureuntil then temperature was <250° C. The samples were then cooled from250° C. to room temperature in an air only flow.

Pelletized samples of the powder catalyst were tested in an apparatus inwhich a gas comprising 500 ppm NO_(x) (NO-only or 1:1 NO:NO₂), 500 ppmNH₃, 14% O₂, 4.6% H₂O, 5% CO₂, with the remainder being N₂ flowed overthe catalyst at a space velocity of 90K/h. The samples were heated fromroom temperature to 150° C. under the above mentioned gas mixture exceptfor NH₃. At 150° C., NH₃ was added in to the gas mixture and the sampleswere held under these conditions for 30 min. The temperature was thenincreased (ramped) from 150 to 500° C. at 5° C./minute.

Fresh and aged NO_(x) (1:1 NO:NO₂) conversion activity profiles overtemperatures from 150° C. to 500° C. are given in FIG. 11. The activityof fresh AFX.Sr—Mn exhibited a T50 (the temperature at which 50%conversion of NO_(x) is achieved) of 205° C. which was 20° C. lower thanthe T50 of AFX.Na—Mn (225° C.). Moreover, AFX.Sr—Mn exhibitedsignificantly enhanced NO_(x) conversions compared to AFX.Na—Mn attemperatures <260° C. (10-60% higher). At temperatures >260° C.,however, AFX.Na.Mn exhibited a slightly higher (˜5%) NO_(x) conversionthan AFX.Sr—Mn. The aged sample of AFX.Sr—Mn once again demonstrated alower T50 at 200° C. than AFX.Na—Mn at 215° C. Furthermore, attemperatures <265° C., aged AFX.Sr—Mn exhibited equal or higher NO_(x)conversions (up to 25% higher) than aged AFX.Na—Mn. Attemperatures >265° C., however, AFX.Na—Mn exhibited equal or slightlyhigher NO_(x) conversions (˜5%) compared to AFX.Sr—Mn.

The concentration of N₂O in gas passing through fresh and aged catalystsover temperatures from 150° C. to 500° C. are given in FIG. 12. Gasflowing into the apparatus contained 500 ppm NO_(x) as 1:1 NO:NO₂. Inthe fresh samples, AFX.Sr—Mn produced a lower N₂O spike (peak value of20 ppm) than AFX.Na—Mn (peak value of 29 ppm). After aging, the peak N₂Olevels for both AFX.Sr—Mn and AFX.Na—Mn decreased slightly. However,AFX.Sr—Mn still produced a lower N₂O spike (peak value of 18.5 ppm) thanAFX.Na—Mn (peak value of 20.5 ppm) in the 150° C. to 260° C. temperatureregime. Only at temperatures >260° C. did the AFX.Sr—Mn produce higheramounts of N₂O than AFX.Na—Mn (˜2-3 ppm higher) after aging.

Fresh and aged NO_(x) (NO-only) conversion activity profiles overtemperatures from 150° C. to 500° C. are given in FIG. 13. The activityof fresh AFX.Sr—Mn exhibited a T50 of 245° C. which was 10° C. lowerthan the T50 of AFX.Na—Mn (255° C.). Furthermore, AFX.Sr—Mn exhibitedenhanced NO_(x) conversion compared to AFX.Na—Mn in the temperaturerange of 150-390° C. (up to 10% higher). At temperatures >390° C., bothsamples showed similar NO_(x) conversions. After aging, both AFX.Sr—Mnand AFX.Na—Mn exhibited a T50 of 250° C. which was similar to the freshperformance. AFX.Sr—Mn, however, displayed equal or enhanced NO_(x)conversions at temperatures <410° C. compared to AFX.Na—Mn (up to 7%higher). At temperatures >410° C., AFX.Na—Mn showed a slightly higherNO_(x) conversion then AFX.Sr—Mn (˜2% higher).

The concentration of N₂O in gas passing through fresh and aged catalystsover temperatures from 150° C. to 500° C. are given in FIG. 14. Gasflowing into the apparatus contained 500 ppm NO_(x) as NO only. In thefresh samples, AFX.Sr—Mn produced more N₂₀ (peak value of 6.5 ppm) thanAFX.Na—Mn (peak value of 5.5 ppm) over the entire temperature range(about 1 ppm higher at any given temperature). After aging, the N₂Olevels for both AFX.Sr—Mn and AFX.Na—Mn increased slightly. However,AFX.Na—Mn still produced less N₂₀ (peak value of 7 ppm) than AFX.Sr—Mn(peak value of 8.5 ppm) over the entire temperature range.

The above results indicated that AFX synthesized in the presence of Sr²⁺rather than Na⁺ resulted in a material with an altered Al distributionin the form of a higher concentration of Al pairs as exhibited by the Cotitration method. Altering this Al distribution facilitated formation ofmore active and selective catalyst sites during typical Fe or Mnexchange techniques. The resulting AFX.Sr—Fe and AFX.Sr—Mn materialsdisplayed a higher activity and typically higher selectivity forreduction of NO_(x) to N₂ in the presence of NH₃ than the analogousmaterials synthesized in Na (AFX.Na—Fe and AFX.Na—Mn, respectively).This enhancement in activity and selectivity is particularly prominentunder equimolar NO:NO₂ conditions (so-called fast SCR conditions).

The above examples are set forth to aid in the understanding of theinvention, and are not intended and should not be construed to limit inany way the invention set forth in the claims which follow hereafter.Although illustrated and herein described with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown, but various modifications may bemade therein without departing from the spirit of the invention.

1. An aluminosilicate zeolite comprising at least about 90% phase pureAFX framework, wherein the aluminosilicate zeolite has a short hexagonalprism morphology.
 2. The aluminosilicate zeolite of claim 1, wherein thealuminosilicate zeolite is free or substantially free of alkaline metal.3. A method for making an aluminosilicate zeolite having a small poreframework comprising reacting a synthesis gel comprising at least onezeolite, a structure directing agent, an alkaline earth metal source,and an optional silica source at a temperature of at least about 100° C.until crystals of the small pore zeolite form.
 4. The method of claim 3,wherein the small pore zeolite crystals are at least about 90% phasepure.
 5. The method of claim 3, wherein the synthesis gel issubstantially free of alkaline metal.
 6. The method of claim 3, whereinthe synthesis gel has one or more of the following compositional molarratios: SiO₂/Al₂O₃ of about 10 to about 80; Na₂O/Al₂O₃ of about 0 toabout 2; M_(AE)O/Al₂O₃ of about 0.3 to about 1.5 (M_(AE) can be Ca, Sr,or Ba); SDA₂O/Al₂O₃ of about 0.7 to about 20; H₂O/Al₂O₃ of about 300 toabout 3000; and OH⁻/SiO₂ of about 0.25 to about 0.5.
 7. The method ofclaim 3, wherein the SDA cation is 1,3-bis(1-adamantyl)imidazolium,N,N-diethyl-cis 2,6-dimethylpiperidinium,N,N-dimethyl-3,5-dimethylpiperidinium,N,N,N-1-trimethyladamantylammonium, orN,N,N-dimethylethylcyclohexylammonium.
 8. A catalyst for treating anexhaust gas comprising a pure phase AFX zeolite that comprises anextra-framework metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo,Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt, and Au, wherein the zeolite has ashort hexagonal prism morphology.
 9. A catalyst article comprising acatalyst according to claim 8 supported on or incorporated into asubstrate selected from a wall-flow honeycomb filter and a flow-throughhoneycomb substrate.
 10. A method for storing NO_(x) comprisingcontacting an exhaust gas stream containing NO_(x) with a catalyst ofclaim
 8. 11. A method for selectively reducing NO_(x) comprisingcontacting an exhaust gas stream containing NO_(x) with a catalyst ofclaim
 8. 12. A method for oxidizing a component of an exhaust gascomprising contacting an exhaust gas stream containing the componentwith a catalyst of claim 8, wherein the component is selected from CO,hydrocarbon, and NH₃.
 13. An aluminosilicate zeolite comprising aframework comprising a number of Al pairs that is at least twice thenumber of aluminum pairs in a reference aluminosilicate zeolitecomprising the same framework, where the reference aluminosilicate wassynthesized using a reaction media comprising an alkali metal.
 14. Thealuminosilicate zeolite of claim 13, wherein the number of pairs isdetermined by Co²⁺ exchange
 15. The aluminosilicate zeolite of claim 13,wherein the aluminosilicate zeolite comprises Ba, Ca, Mg, Sr, or acombination thereof.
 16. The aluminosilicate zeolite of claim 13,wherein the aluminosilicate zeolite is free or substantially free ofalkaline metal.
 17. The aluminosilicate zeolite of claim 13, wherein thenumber of Al pairs is at least three, four, five six or seven times thenumber of aluminum pairs in a reference aluminosilicate zeolitecomprising the same framework.
 18. The aluminosilicate zeolite of claim13, wherein the framework is a small pore framework.
 19. Thealuminosilicate zeolite of claim 18, wherein the framework is AEI, AFXor CHA.
 20. The aluminosilicate zeolite of claim 13, wherein thealuminosilicate zeolite has a silica-to-alumina ratio of about 10 toabout 50, about 10 to about 30, or about 15 to about
 25. 21. A catalyticarticle comprising a substrate and an aluminosilicate zeolite of claim13.
 22. A system comprising a catalytic article of claim
 21. 23. Amethod of making the aluminosilicate zeolite of claim 16, the methodcomprising reacting a synthesis gel comprising at least one zeolite oran alkali free alumina source, a structure directing agent, an alkalineearth metal source, and an optional silica source at a temperature of atleast about 100° C. until crystals of the small pore zeolite form. 24.The method of claim 23, further comprising removing the alkaline earthmetal to form an ammonium or hydrogen form.
 25. The method of claim 23,further comprising introducing a promoter metal into the zeolite as anextra-framework metal.
 26. The method of claim 24, wherein the smallpore zeolite is selected from the group consisting of AFX, AEI, and CHA.27. The method of claim 23, wherein the alkaline earth metal is selectedfrom the group consisting of Sr, Ba, and a combination thereof.
 28. Themethod of claim 23, wherein the synthesis gel is free or substantiallyfree of alkaline metal.
 29. The method of claim 23, wherein thesynthesis gel has one or more of the following compositional molarratios: SiO₂/Al₂O₃ of about 10 to about 80; Na₂O/Al₂O₃ of about 0 toabout 2; M_(AE)O/Al₂O₃ of about 0.3 to about 1.5 (M_(AE) can be Ca, Sr,or Ba); SDA₂O/Al₂O₃ of about 0.7 to about 20; H₂O/Al₂O₃ of about 300 toabout 3000; and OH⁻/SiO₂ of about 0.25 to about 0.5.
 30. The method ofclaim 23, wherein the SDA comprises a cation selected from the groupconsisting of 1,3-bis(1-adamantyl)imidazolium, N,N-diethyl-cis2,6-dimethylpiperidinium, N,N-dimethyl-3,5-dimethylpiperidinium,N,N,N-1-trimethyladamantylammonium, andN,N,N-dimethylethylcyclohexylammonium.
 31. A method for increasing thenumber of Al pairs in a zeolite that is at least twice the number ofaluminum pairs in a reference aluminosilicate zeolite comprising thesame framework, the method comprising increasing the ratio of alkalineearth metal source to the alkali.
 32. The method of claim 31, whereinthe step of increasing the ratio of alkaline earth metal source to thealkali comprises reacting a synthesis gel comprising at least onezeolite or an alkali free alumina source, a structure directing agent,an alkaline earth metal source, and an optional silica source at atemperature of at least about 100° C. until crystals of the small porezeolite form.
 33. A method of increasing the catalytic activity of asmall pore zeolite, the method comprising forming a small pore zeolitecomprising a framework having an increased number of Al pairs comparedto a comparable zeolite produced using an alkali metal.
 34. The methodof claim 33, further comprising introducing a promoter metal into thezeolite as an extra-framework metal.